1. Field of the Invention
This invention relates to shift control mechanisms for a change speed transmission or transmission section, such as the auxiliary section of a compound transmission, having selectively axially movable gears, such as mainshaft gears, the selective axial movement of which is effective to cause engagement and disengagement of the axially moved gear with a shaft or a complementary gear. Preferably, the shift control mechanism is utilized for a constant mesh four speed transmission or transmission section, such as an auxiliary transmission section, having a remote master control or valve and a slave control and having four selectively axially movable constantly meshed gears which are selectively clutchable, one at a time, to a shaft by means of resiliently engageable, blocked jaw clutch structures.
2. Description of the Prior Art
Compound constant mesh transmissions of the splitter or range type, or a combination thereof, are well known in the prior art as may be seen by reference to U.S. Pat. Nos. 3,105,395; 3,648,546; 3,799,002; 2,932,988 and 3,229,551, all hereby incorporated by reference.
Blocked change gear transmissions of both the simple and the compound types which utilize selective axial movement of selectively axially movable constant mesh gears to cause engagement of the axially moved gear are also well known in the prior art as may be seen by reference to U.S. Pat. Nos. 3,799,002; 3,921,469; 3,924,484; 3,983,979; 4,192,196 and 4,194,410, all of which are hereby incorporated by reference.
Compound transmissions of the splitter type utilizing a main transmission section having axially fixed gears engaged by manual, nonsynchronized, nonblocked jaw clutch assemblies and a four speed splitter type auxiliary transmission section utilizing blocked resiliently shifted jaw clutch assemblies and selectively axially movable constantly meshed auxiliary section mainshaft gears are seen in copending application Ser. No. 287,470, filed July 27, 1981 and assigned to the assignee of this invention.
In the design of transmissions, particularly heavy duty transmissions, such as used in trucks, there has existed for a long time the problem of shifting the transmission to the various speed ratios, which problem is even greater when the transmission is compounded, that is provided with an auxiliary transmission section of the range or the splitter type for increasing the number of speed ratios. In most known transmissions, the shifting process is either relatively difficult and/or the shifting mechanism is relatively complex. Thus, there has been a continuing effort in the design of transmissions to improve the shifting, to improve the rapidity of shifting, to reduce the complexity of the shifting mechanism, and to reduce its weight, space requirements and costs. Hence, without detracting in any way from the operability or desirability of many of the shifting mechanisms previously known, it may be stated that in the present invention these general objectives are accomplished to even a greater degree than has been previously possible.
Compound transmissions, such as the transmission disclosed in the above-mentioned copending application Ser. No. 287,470, filed July 27, 1981 and hereby incorporated by reference, utilizing a conventional nonsynchronized, nonblocked main section and a blocked auxiliary section is believed to be a highly desirable design. However, if the blocked auxiliary section is provided with a relatively large number of selectable speeds or ratios, such as four or more, the axial space requirements may become undesirably large as such auxiliary transmission sections typically utilized in a plurality of axially coupled pairs of mainshaft gears controlled by a single shift fork, or if separate shift forks and shift rails are provided the slave valve shift bar valve housing and required interlock structure may become unduly large or complicated. This is because the space required to allow axial shifting of a gear, such as a mainshaft gear, is often considerably greater than the space required to allow axial movement of a jaw clutch collar as typically utilized in a nonsynchronized, nonblocked (i.e. so called "clash type") transmission.